BRACHIOPODA. 85 



and long ; muscular impression moderate, posterior, not hollowed. 

 White, purplish round the margin. Attached to rocks. Diameter 

 about 2 or 3. 



The common rock oyster of the North Island, 



Class Braehiopoda. 



Body protected by a bivalve shell, applied to the dorsal and ventral 

 surfaces of the animal ; dorsal valve smaller, ventral with its umbo 

 produced and perforated ; mouth with two long cirriferous arms ; 

 animal attached by a peduncle. 



OIIDER ANCYLOBRACHIA. 



Oral arms attached to two shelly plates arising from the cardinal 

 edge of the ventral valve, recurved and convolute on the inner side of 

 the lamina ; shell perforated. 



FAMILY TEREBRATULID^. 



Shell minutely punctate, usually round or oval ; foramen separated 

 from the hinge line by a small triangular plate or deltidiuin composed 

 of two pieces, teeth two, curved ; dorsal valve with a prominent cardi- 

 nal process between the dental sockets, and a slender shelly loop. 



WALDHEIMIA. 



Foramen complete ; loop elongated and reflected, attached to the 

 hinge plate ;, median septum of the smaller valve elongated. 



1. W. lentiCUlariS, Deshayes, Mag. Zool, 1841, t. 41. Orbi- 

 cular, smooth, red ; margins even ; beak small, recurved ; foramen 

 small; deltidiuni conspicuous; loop elongated, reflected. Length, 2 ; 

 breadth, T83 ; height, 1T7. 



Common. 



TEREBRATELLA. 



Loop elongated, reflected, attached to the hinge plate, and also to 

 the longitudinal septum by processes given off at right angles from 

 the crura, near the centre of the valve. 



2. T. cruenta, Dilhvyn ; T. sanguined, Lamark ; T. rulra, Sow- 

 erly ; T. zealandica, Desliayes. Rounded, ventricose, ornamented with 

 radiating dichotoinous ribs ; orange-red, deepest at the lines of growth ; 

 margins creuulatcd ; dorsal valve with a central, longitudinal depres- 

 sion ; beak somewhat produced, lateral ridges distinct ; area large, 



'rounded; foramen large, complete; deltidiuin large; loop elongated, 

 doubly attached. Length, 1'5 ; breadth, 1'G ; height, 1. 

 Cook Strait. 



3. T. rubicunda, Solander; T. inconspicua, Soiverby. Bounded, 

 trilobed, gibbous, smooth, yellow-red, deeper at the lines of growth ; 



